Electric-current-dependent resistance has been studied in epitaxial thin films of La 0.7 Ca 0.3 MnO 3 and La 0.85 Ba 0.15 MnO 3. Attention was focused at the influence of the applied dc current on the resistance of these epitaxial thin films in the absence of a magnetic field. A significant change in the ratio of the peak resistance at different currents or current resistance was found to be ϳ23%-26% with a current density up to 8ϫ10 4 Acm Ϫ2. For both La 0.7 Ca 0.3 MnO 3 and La 0.85 Ba 0.15 MnO 3 compounds, the dependence of the measured resistance on the current revealed a good linear relationship. Although the nature behind such an effect has not been well understood yet, the feature that the resistance in doped manganese oxides could be easily controlled by the electric current should be of interest for various applications such as field effect devices.

Structure, transport properties, and electronic structure of epitaxial thin films La 0.9 Sn 0.1 MnO 3 and La 0.9 Ca 0.1 MnO 3 have been experimentally studied. According to the Hall-effect measurement, La 0.9 Sn 0.1 MnO 3 is an n-type conductor in the metallic state due to the substitution of Sn for La. X-ray photoelectron spectroscopy spectra revealed a shift of the Fermi level and the Mn ionic core level of La 0.9 Sn 0.1 MnO 3 in comparison with La 0.9 Ca 0.1 MnO 3. The difference between the Mn-2p spectra of La 0.9 Sn 0.1 MnO 3 and La 0.9 Ca 0.1 MnO 3 implies that Mn ions in the former are at a Mn 2ϩ /Mn 3ϩ mixed-valence state, which is significantly different from the divalent-element-doped manganese oxides, where the Mn ions are in the mixed-valence state of Mn 3ϩ /Mn 4ϩ .